Cenozoic potassic-ultrapotassic igneous rocks are widespread in the southeastern Tibetan Plateau.Their petrogenesis and magmatic processes remain subject to debate in spite of numerous publications.Almost all of the C...Cenozoic potassic-ultrapotassic igneous rocks are widespread in the southeastern Tibetan Plateau.Their petrogenesis and magmatic processes remain subject to debate in spite of numerous publications.Almost all of the Cenozoic extrusive and intrusive rocks in the Yao’an area,western Yunnan Province,SW China,are geochemically shoshonitic,collectively termed here the Yao’an Shoshonitic Complex(YSC).The YSC is located in the(south)easternmost part of the ENE-WSW-trending,~550 km-long and~250 km-wide Cenozoic magmatic zone;the latter separates the orthogonal and oblique collision belts of the India-Eurasia collision orogen.Previously published geochronological and thermochronological data revealed that the rocks of the YSC were emplaced over a short timespan of 34-32 Ma.This and our new data suggest that the primary magma of the YSC likely was formed by partial melting of ancient continental lithospheric mantle beneath the Yangtze Block.This part of the continental lithospheric mantle had likely not been modified by any oceanic subduction.Fractionation crystallization of an Mg-and Ca-bearing mineral and TiFe oxides during the magmatic evolution probably account for the variable lithologies of the YSC.展开更多
In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed stratigraphical data of the Late Oligocene-Early...In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed stratigraphical data of the Late Oligocene-Early Miocene diagnostic species thus obtained. The nannofossil zonation of this interval was subdivided and the Oligocene-Miocene boundary was further determined. Several last Late Oligocene events were recognized, indicating a long-term sedimentary hiatus in the uppermost Upper Oligocene. The time span of the hiatus was estimated for about 2.2 Ma, at least from 23.9 to 26.1 Ma. The lithological and geophysical data from Site 1148 indicate some abrupt sedimentary changes that occurred below and above the hiatus. This hiatus at Site 1148 was probably related to the tectonic change, a major ridge jump during the seafloor spreading in the Late Oligocene South China Sea.展开更多
Oil and gas exploration prospect for the Miocene and Late Oligocene strata in Qiongdongnan（琼东南） basin are evaluated.The structural-sedimentary and reservoir characteristics are discussed and helpful conclusions a...Oil and gas exploration prospect for the Miocene and Late Oligocene strata in Qiongdongnan（琼东南） basin are evaluated.The structural-sedimentary and reservoir characteristics are discussed and helpful conclusions are drawn.It was proved that there are mainly two reservoir and capping assemblages in Qiongdongnan basin by drilled wells,i.e.,one assemblage of the second and the third members of Lingshui（陵水） Formation,upper Sanya（三亚） and Meishan（梅山） formations.According to hydrocarbon evaluation from burial history and well data,all source rocks in Yacheng（崖城） and Lingshui formations have reached the mature-overmature stage.High temperature and overpressure provide dynamic conditions for oil and gas migration,while the long-term activity of basin controlling faults is adverse to their accumulation in upheaved areas.However,because the secondary faults in the basin ceased their activities at the end of the Sanya Period,and the Sanya Formation was later covered by the regional overlying layer of the Meishan Formation,the blocks and low uplifts near the secondary faults were favorable for oil and gas accumulation.Furthermore,as another important pointed area for gas migration,the highest position of a structural ridge should reasonably be a range that is covered by marine mudstone or sandy mudstone during the whole subsiding period,and therefore,the reservoir bed should not be in that position but at its inferior eminence or adjacent slope zone.Therefore,we can draw a conclusion that the inferior low uplifts and structural ridges rather than the upheavals or the top of a structural ridge,probably,have huge reservoirs,and should be chief exploration targets in the Qiongdongnan basin.展开更多
Paraceraterium sui sp.nov. is represented by a lower jaw collected at Loc.20004 (46°35.779′N , 87°43.818′E) of Saerduoyila, Halamagai Village, Fuhai County, Xinjiang Uygur Autonomous Region. The new specie...Paraceraterium sui sp.nov. is represented by a lower jaw collected at Loc.20004 (46°35.779′N , 87°43.818′E) of Saerduoyila, Halamagai Village, Fuhai County, Xinjiang Uygur Autonomous Region. The new species is similar to the type species of the genus, P. bugtiense , in general morphology of the mandible and teeth, but differs from the latter in larger size, the proportionally deeper horizontal ramus, the more anteroventrally curved symphysis and the much deeper trenched dorsal surface of symphysis. The associated small mammals indicates an age of Late Oligocene. The occurrence of Para ceratherium sui demonstrates that the genus Paraceratherium erected by Forster Cooper, based on the lower jaw from Pakistan, is a valid taxon different from Indricotherium .展开更多
基金financially supported by the Ministry of Sciences and Technology of China(Grant No.2022YFF0800901)the Natural Science Foundation of China(Grant Nos.92055206 and 42163007)。
文摘Cenozoic potassic-ultrapotassic igneous rocks are widespread in the southeastern Tibetan Plateau.Their petrogenesis and magmatic processes remain subject to debate in spite of numerous publications.Almost all of the Cenozoic extrusive and intrusive rocks in the Yao’an area,western Yunnan Province,SW China,are geochemically shoshonitic,collectively termed here the Yao’an Shoshonitic Complex(YSC).The YSC is located in the(south)easternmost part of the ENE-WSW-trending,~550 km-long and~250 km-wide Cenozoic magmatic zone;the latter separates the orthogonal and oblique collision belts of the India-Eurasia collision orogen.Previously published geochronological and thermochronological data revealed that the rocks of the YSC were emplaced over a short timespan of 34-32 Ma.This and our new data suggest that the primary magma of the YSC likely was formed by partial melting of ancient continental lithospheric mantle beneath the Yangtze Block.This part of the continental lithospheric mantle had likely not been modified by any oceanic subduction.Fractionation crystallization of an Mg-and Ca-bearing mineral and TiFe oxides during the magmatic evolution probably account for the variable lithologies of the YSC.
文摘In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed stratigraphical data of the Late Oligocene-Early Miocene diagnostic species thus obtained. The nannofossil zonation of this interval was subdivided and the Oligocene-Miocene boundary was further determined. Several last Late Oligocene events were recognized, indicating a long-term sedimentary hiatus in the uppermost Upper Oligocene. The time span of the hiatus was estimated for about 2.2 Ma, at least from 23.9 to 26.1 Ma. The lithological and geophysical data from Site 1148 indicate some abrupt sedimentary changes that occurred below and above the hiatus. This hiatus at Site 1148 was probably related to the tectonic change, a major ridge jump during the seafloor spreading in the Late Oligocene South China Sea.
基金supported by the Key Project of the National Eleventh Five-Year Plan of China (No. 2008ZX05023-004)
文摘Oil and gas exploration prospect for the Miocene and Late Oligocene strata in Qiongdongnan（琼东南） basin are evaluated.The structural-sedimentary and reservoir characteristics are discussed and helpful conclusions are drawn.It was proved that there are mainly two reservoir and capping assemblages in Qiongdongnan basin by drilled wells,i.e.,one assemblage of the second and the third members of Lingshui（陵水） Formation,upper Sanya（三亚） and Meishan（梅山） formations.According to hydrocarbon evaluation from burial history and well data,all source rocks in Yacheng（崖城） and Lingshui formations have reached the mature-overmature stage.High temperature and overpressure provide dynamic conditions for oil and gas migration,while the long-term activity of basin controlling faults is adverse to their accumulation in upheaved areas.However,because the secondary faults in the basin ceased their activities at the end of the Sanya Period,and the Sanya Formation was later covered by the regional overlying layer of the Meishan Formation,the blocks and low uplifts near the secondary faults were favorable for oil and gas accumulation.Furthermore,as another important pointed area for gas migration,the highest position of a structural ridge should reasonably be a range that is covered by marine mudstone or sandy mudstone during the whole subsiding period,and therefore,the reservoir bed should not be in that position but at its inferior eminence or adjacent slope zone.Therefore,we can draw a conclusion that the inferior low uplifts and structural ridges rather than the upheavals or the top of a structural ridge,probably,have huge reservoirs,and should be chief exploration targets in the Qiongdongnan basin.
文摘Paraceraterium sui sp.nov. is represented by a lower jaw collected at Loc.20004 (46°35.779′N , 87°43.818′E) of Saerduoyila, Halamagai Village, Fuhai County, Xinjiang Uygur Autonomous Region. The new species is similar to the type species of the genus, P. bugtiense , in general morphology of the mandible and teeth, but differs from the latter in larger size, the proportionally deeper horizontal ramus, the more anteroventrally curved symphysis and the much deeper trenched dorsal surface of symphysis. The associated small mammals indicates an age of Late Oligocene. The occurrence of Para ceratherium sui demonstrates that the genus Paraceratherium erected by Forster Cooper, based on the lower jaw from Pakistan, is a valid taxon different from Indricotherium .
